1. Field of the Invention
The present invention relates to a process for supplying a rare earth metal-based alloy powder to a cavity in a mold, for example, in order to subject the rare earth metal-based alloy powder to a pressing for producing a rare earth metal-based magnet, and to an apparatus suitable for use in such process. More particularly, the present invention relates to a powder supplying process which is capable of uniformly supplying and filling, into a cavity, even an alloy powder which is poor in flowability and difficult to be filled in a cavity and moreover, is inflammable and difficult to handle, as is the above-described rare earth metal-based alloy powder, without production of agglomerates and bridges and without occurrence of inflammation.
2. Description of the Related Art
To supply a powder poor in flowability from a feeder box into a cavity in a mold, a supplying apparatus is conventionally used, which is designed so that a feeder box having an opening in its bottom is moved to above a cavity defined in a mold, whereby a rare earth metal-based alloy powder is supplied from the feeder box into the cavity. There are such conventionally known powder supplying apparatus in which a rotary blade rotated in the feeder box is used as described in Japanese Patent Application Laid-open No.59-40560; a spherical member rotated in the bottom of the feeder box, as described in Japanese Patent Application Laid-open No.10-58198; or a rotary blade rotated spirally within the feeder box is used, as described in Japanese Utility Model Application Laid-open No.63-110521.
In the above prior art systems, however, the height of the feeder box is increased, and the stroke of a punch is prolonged. Therefore, the time taken for one run of the pressing is prolonged, resulting in a reduced productivity. A powder poor in flowability such as a rare earth metal-based alloy powder cannot be filled uniformly into the cavity, if a uniform urging force is not provided. Particularly, a rare earth metal-based alloy powder produced by a strip casting process and having an excellent magnetic characteristic is extremely poor in flowability and difficult to be filled uniformly into the cavity, because it has a small average particle size and a narrow and sharp distribution of particle sizes. Further, when a lubricant such as a fatty ester for enhancing the orientation is added, the alloy powder has an increased viscosity, and hence, is more difficult to be filled uniformly into the cavity.
In addition, in the apparatus having the above-described arrangement, there is a possibility that the rare earth metal-based alloy powder is exposed to the atmosphere to become inflamed, because each of the die surface and the bottom of the feeder box is formed of a metal, and the alloy powder is sometimes caught between them.